Entomology and Nematology Department, University of Florida, 1881 Natural Area Drive, Gainesville, FL 32611, USA.
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
Proc Biol Sci. 2019 Aug 14;286(1908):20190906. doi: 10.1098/rspb.2019.0906. Epub 2019 Jul 31.
Sexually selected weapons are assumed to trade off with traits related to ejaculates, such as testes. However, remarkably little is known about what governs resource allocation and why trade-offs are found in some cases and not others. Often-used models depict competitive allocation occurring within the functional grouping of traits (e.g. reproduction); however, other factors including tissue expense and developmental timing may influence allocation. Experimental comparisons of investment across the sexes have the potential to illuminate allocation rules, because the sexes do not always use traits for the same functions. Here, we capitalize upon a species where females have weapons-testes homologues. We report that a documented trade-off in investment between hind-limb weapons and testes in leaf-footed cactus bugs, Narnia femorata, is even more pronounced in female hind limbs and ovaries. Female hind limbs in this species do not share the clear reproductive function of male hind limbs; therefore, this trade-off spans trait functional groups. Such patterns of investment suggest that future studies of reproductive trade-offs should consider factors such as tissue expense and developmental timing.
性选择武器被认为与精液相关的特征（如睾丸）存在权衡关系。然而，对于资源分配的规律以及为什么在某些情况下会出现权衡关系，我们知之甚少。常用的模型描绘了在特征的功能分组内发生的竞争分配（例如生殖）；然而，其他因素，包括组织消耗和发育时间，可能会影响分配。在两性之间进行投资的实验比较有可能阐明分配规则，因为两性并不总是将特征用于相同的功能。在这里，我们利用一种雌性具有武器-睾丸同源物的物种。我们报告称，在叶足仙人掌虫 Narnia femorata 中，后肢武器和睾丸之间投资的已有记录的权衡关系在雌性后肢和卵巢中更为明显。在这个物种中，雌性后肢没有雄性后肢的明显生殖功能；因此，这种权衡关系跨越了特征功能组。这种投资模式表明，未来对生殖权衡的研究应该考虑组织消耗和发育时间等因素。
